1. Field of the Invention
The present invention relates to an antenna, and more particularly to a circularly polarized antenna that a dielectric substrate, a ground plane and a radiating patch. The circularly polarized antenna set in a portable wireless product has a maximum gain when the portable wireless product is used and held uprightly.
2. Description of Related Art
Circularly polarized signals may be transmitted through ionosphere so that military satellites use circularly polarized antennas to transmit circularly polarized signal. Since the global positioning system (GPS) of satellites is recently available for the public, GPS products are equipped with circularly polarized antennas. Furthermore, circular polarized antennas have an excellent advantage that prevents multi-signal transmission path interference so that circularly polarized antennas are also used in general wireless products such as cellular phones and wireless internet routers.
With reference to FIG. 1, a conventional circularly polarized antenna comprises a substrate (1), a ground plane and a radiating patch.
The substrate (1) has a front surface and a rear surface. The ground plane is mounted on the rear surface. The radiating patch is rectangular, mounted on the front surface of the substrate (1) and has two opposite bevel corners (11), a feeding point (10) and two current paths (P1, P2). The currents along the current paths (P1, P2) stimulate two operating modes being perpendicular to each other to provide circularly polarized signals.
With reference to FIG. 2, another circularly polarized antenna comprises a substrate (2), a ground plane, a connecting member (22) and a radiating patch (20). The substrate (2) has a front surface and a rear surface. The ground plane is mounted on the rear surface of the substrate (2). The connecting member (22) is branched, is mounted on the front surface of the substrate (2) and has a feeding point (21) and two branches. The feeding point (21) is connected to a printed circuit board from a wireless product. Each branch has a feeding end (23). The radiating patch (20) is connected to the feeding ends (23) of the connecting member (22) and is suspended on the front surface of the substrate (2). The radiating patch (20) cooperates with the connecting member (22) to provide two operating modes to transmit circularly polarized signals.
However, the two aforementioned conventional circularly polarized antennas are set uprightly with the ground plane and radiating patch perpendicular to the ground when mounted on portable devices such as cellular phones or GPS devices. Without setting the ground plane and radiating patch parallel to the ground, signal transmission efficiency of the conventional circularly polarized antennas is greatly lowered.
To overcome the shortcomings, the present invention provides a circularly polarized antenna to mitigate or obviate the aforementioned problems.